I have strong smell of gas and I cannot figure out where the leak is. I see on online that several gas leak detectors are available. Prices start at $120. Anybody have experience with these instruments. VG 30 engine......

The gas tank on the 510 had a recall from the factory way back when. There are 2 fittings on the bottom of the tank that were capped from the factory. These caps rot out over time. If you pull the back seat, you should be able to see them and/or a puddle under there. Check that first.

The late wagon tanks with the "evaporative emissions" stuffs have a bazillion hoses to rot and fail and leak and stink...

Pre-evap type

datsun 510 wagon gas tank simple.png (248.79 KiB) Viewed 619 times

Post-evap type

datsun 510 wagon gas tank complex.png (239.39 KiB) Viewed 619 times

In the second picture, look specifically at item #23 "ASSY-TANK RESERVOIR, WAGON EVAPO" and at all of the rubber hoses that connect it to the gas tank. A nightmare of rotten hoses!

Rumor has it that some people turn the post-evap setups into pre-evap setups by removing #23 and then welding various ports closed on the gas tank (but I would imagine that you must retain some kind of vent tube like #6 in the first picture!). There is also the issue of vented gas caps on wagons

I know I did seal up these evap lines on my late wagon, missed the fact that the cap wasn't vented and collapsed my tank in a 45 minute drive, so beware.

Hoses #26 in the second drawing are very prone to failure and are an absolute PITA to access as they go through a hole in the bodywork in the car. I have had to replace these on a different wagon and it was a nightmare as access with my large hands just wasn't there.

Also, your car has been converted to EFI, what was done to the send and return lines at the tank? I know this was an issue when I did the EFI conversion on my second wagon. I ended up removing these and welding in a larger one for the feed line. Just in case this hasn't been done, and you end up removing the tank to fix the other hoses anyways....

If you're going to explore in the area of the wagon gas tank and associated hoses, do yourself a favor and pressure-wash the underside of your car. Decades of road grime will rain down on you as you wiggle hoses.

DQ 9.1 documents both the early and late fuel systems and hoses for replacement. Worst job I ever did on a 510.

Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

Should be fairly obvious if the fuel smell is coming from the VG/engine compartment or from the gas tank area. If you've eliminated the stock evap system, then you've reduced the number of joints by a lot. Going over each and checking the tension on the clamps shouldn't take long. Is it worse when the tank's full, cold/hot, left hand turns, etc.?

To your OP, I'd spend an hour checking over connections before dropping $120 on a detector gadget. And if you still couldn't find the source, better smog testing shops used to have those detectors to sniff out evap/emissions leaks.

Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson